ABS and Brake light comes on while driving, what does that mean?

02 Burb Z71 with 195,000 miles. It seems to happen whether in auto 4wd or high 2wd. There's no wiggle in the steering or when I had the front wheels up I shook them to see if the bearings were bad. This truck lived a while in Utah so it could have some rust hidden somewhere. Any thoughts???

That's just what I was about to say. Check the brake fluid level. If the brakes were just replaced, it could also be an indicator that the brakes need to be bled, too. Does your brake pedal tend to go almost to the floor?

Did you change to a non-OEM tire size (overall diameter) and tweak the computer (with a tuner)???

I ask becaue the ABS and Brake light also come on, together, when a tuner has been used to tell the computer about a tire size (overall diameter) the truck doesn't care for. GM trucks are finicky about this and it usually takes some trial/error to find a size that's close that the computer will accept.

You need to use a handheld tuner to tell the truck the new tire size OR see the dealership and have them do it. (Keep in mind that your speedo will read slower than you're actually going until you address this! Be wary of tickets...)

I'm a strong proponent of owning a tuner because you get to keep it and do other things with it -- whereas a visit to the dealership costs you cash and does nothing else for you. I'm also a strong proponent of DiabloSport tuners because you can work with someone who develops custom tunes to get something really specific to your truck -- which may (and likely will) help your fuel mileage -- which means the tuner and custom tune pay for themselves over time. (06monteSS is one such developer of custom tunes and he's a sponsor on this site. He did my tune and I'm very pleased with the results. He bundles tuners and custom tunes, too -- for a cost less than they would be if bought separately. He's also good with those who aren't terribly tech savvy. PM him if you have questions.)

If you go the tuner route you will need to play with the tire size settings until you find one that is close to yours that the truck will accept without turning on the idiot lights. For example, my tires are technically 34.3" in overall height. The closest setting for me would be 34.5", but I continued to get idiot lights with this, so I then tried 34" and the truck liked that -- no lights since.